Atrial Fibrillation Clinical Trial
Official title:
A Comparison of Two Biphasic Waveforms and Impact of Oxygen on Myocardial Injury Following Cardioversion
Background:
Cardiac arrhythmias can be terminated by electrical current applied by an external
defibrillator. This treatment, named cardioversion, has been used for decades in the
treatment of atrial fibrillation.
Several kinds of defibrillators exist, though the relative efficacy and safety of these
defibrillators is not clear.
During cardioversion, oxygen is being administered, and it has been a long-held belief that
oxygen is always beneficial for the patient. This is now being challenged by recent studies
suggesting excessive oxygenation to be potentially dangerous for the patients.
Objective:
1. To compare the efficiency and safety of two different defibrillators
2. To investigate the effects of excessive oxygen on injury of the heart following
cardioversion.
Experimental design:
Patients will be recruited at the outpatient clinic at the Department of Cardiology, Regional
Hospital of Randers, Denmark as a part of the pre-cardioversion check.
Patients will be randomized to cardioversion using one of two defibrillators and randomized
to treatment with room air or 100% oxygen.
The cardiac condition will be measured by blood samples before cardioversion, 4 hours after
cardioversion and 3 months after cardioversion. Heart rhythm will be measured by ECG before
cardioversion, 1 minute-, 30 minutes- and 4 hours after cardioversion.
Background:
Treatment of cardiac arrest includes effective chest compressions, ventilation using high
flow oxygen and the delivery of electric shocks (cardioversion). Prompt termination of
cardiac arrhythmias and sufficient airway handling including oxygenation are crucial factors
for patient outcome. Studies suggest that cardioversion itself may induce myocardial injury;
however it is currently unknown whether hyperoxia exacerbate this injury.
Currently, several different biphasic waveforms are in use for cardioversion.The comparative
efficacy and safety of these waveforms has not been compared in clinical studies.
Commercially available defibrillators use different electrical waveforms that may affect the
efficacy of external defibrillation. Although the superiority of biphasic over monophasic
waveforms is well established, the relative efficacy and safety of the available biphasic
waveforms is not clear.
The long held belief that oxygen (O2) is always beneficial for ill and injured patients is
being challenged by recent studies suggesting that excessive oxygenation may result in
free-radical mediated tissue damage, resulting in increased morbidity and mortality. Recent
guidelines suggest that O2 should be 'titrated' to achieve an appropriate target saturation
of 94-98% rather than being administered in an all-or-nothing fashion, particularly in
patients with myocardial ischemia or those following resuscitation from cardiac arrest. The
Scottish Intercollegiate Guidelines Network (SIGN), British Thoracic Society, National
Institute of Health Care Excellence (NICE), European Resuscitation Council and other
respected bodies all restrict O2 use to those with hypoxemia, pulmonary oedema or continuing
myocardial ischemia, based on expert opinion and pathophysiological reasoning rather than
hard evidence.
Studies using patients presenting with shockable life-threatening arrhythmias (e.g.
ventricular fibrillation) are difficult to perform for ethical and practical reasons. This
study will therefore use patients requiring elective cardioversion for atrial arrhythmias,
who are able to give consent and also present a more controlled population. Elective
cardioversion is a standard treatment for patients with atrial arrhythmias and is performed
as a day case procedure under general anaesthesia.
This study has the following aims:
1. To compare a standard biphasic waveform with a newer pulsed biphasic waveform on which
there is little published data
2. To compare the effect of hyperoxia and room air on myocardial injury following
cardioversion on which there is no published data.
Methods:
All patients admitted for cardioversion for atrial fibrillation and flutter will be
potentially eligible for the study. Patients will be recruited at the Regional Hospital of
Randers as a part of the pre-cardioversion check. This is the first contact to patients, and
they will receive oral and written information. The oral and written information will be
given by a doctor and/or the primary investigator. The information will be given in a quiet
setting, and the patients may ask questions about the study. It will be possible for the
patient to have a companion present. Informed consent will be obtained from all participants
during the pre-cardioversion check or alternatively prior to cardioversion allowing the
patient to have a companion present before consent is given. Patients declining to
participate in the study will receive treatment according to the standard protocol.
Patients with atrial fibrillation or flutter for ≤48 hours may be cardioverted immediately.
Patients with atrial fibrillation or flutter for >48 hours will be required to have a
documented weekly international normalized ratio (INR) ≥2.0 (including within 48 hours of
cardioversion) or treatment with dabigatranetexilat for three weeks or longer. Alternatively,
a transoesophageal echocardiogram documenting absence of intracardiac thrombi is accepted and
cardioversion can be performed on treatment with low molecular weight heparin. All patients
will be discharged with a recommendation for therapeutic anticoagulation according to current
guidelines.
Patient preparation
Patients will be consulted prior to cardioversion; standard blood test will be taken, blood
pressure, height and weight will be measured. Information from patient chart (age, gender,
morbidity, co-morbidity and medication) will be used to define baseline values. In addition
New York Heart Association Functional Classification (NYHA), European Heart Rhythm
Association AF-related symptoms (EHRA), American Society of Anaesthesiologists Score (ASA)
and Canadian Cardiovascular Society Grading System (CCS) will be recorded during history
taking. In addition, information from the patient chart regarding comorbidities, medication
etc. will be obtained.
Cardioversion protocol
Blood samples, ECG, blood pressure, oxygen saturation and heart rate will be obtained at
baseline and all patients will receive 0.5 mg Rapifen i.v. All patients will be treated with
100 % oxygen or room air, 10-15 L/ minute for 3 minutes before administration of Propofol.
All patients will be treated with Propofol 1 mg i.v./kg bodyweight with subsequent 20 mg
boluses as needed. Before cardioversion PaO2 will be measured by arterial blood gas (1 mL).
Follow up All patients will be seen at the outpatient clinic after 3 months. Echocardiography
will be performed and biomarkers will be measured. Patients will be classified after NYHA,
EHRA, ASA and CCS.
Statistics
Regarding waveforms: Assuming the cumulative efficacy, defined as success rate after all
delivered shocks, for one of the waveforms is 95%, and for the other waveform ≥80%, a sample
size of 75 patients in each group is needed to achieve a power of 80% in rejecting the null
hypothesis (that the difference in cumulative efficacy is ≥15%). Continuous variables (number
of shocks, delivered energy etc.) are expressed as mean ± SD or median values and compared
with Students t-test or equivalent non-parametric test. Categorical variables (e.g.
successful cardioversion) are expressed as percentages and compared using the Chi-square or
Fisher's exact test (where appropriate). P ≤ 0.05 is considered statistically significant for
all comparisons.
Regarding oxygen treatment: It is estimated that 150 patients will be sufficient for the
study. After treatment of 60 patients, an interim futility test will be performed. Biomarker
data will be analyzed using parametric and non-parametric tests as appropriate. P ≤ 0.05 is
considered statistically significant.
Ethics
Approval from The Danish Research Ethics Committee and Danish Data Protection Agency has been
obtained. The project will be performed in accordance with the Danish Health Act.
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